Note: Descriptions are shown in the official language in which they were submitted.
CA 02275391 1999-06-16
-1-
SPECIFICATION
FILE PROCESSING METHOD, DATA PROCESSING
APPARATUS AND STC>RAGE MEDIUM
TECHNICAL FIELD
The present invention generally relates to
file processing methods, data processing apparatuses
and storage mediums, and more particularly to a file
processing method and a data processing apparatus
which compress a file such as a dictionary file
related to one or a plurality of dictionaries,
encyclopedias and the like, store the compressed
file in a storage medium and read the stored file
from the storage medium, and to a storage medium
which stores a file such as a compressed dictionary
file.
Recently, there are storage mediums such
as a CD-ROM which prestores information related to a
dictionary, encyclopedia or the like. By making
access to such a CD-ROM fo~om a computer, it is
possible to read and display the information related
to the dictionary, encyclopedia or the like. As a
result, a large amount of information related to the
dictionary, encyclopedia or the like can be stored
in a single CD-ROM which is extremely compact. In
addition, instead of obtaining the necessary
information by opening a dictionary, encyclopedia or
the like while using a computer, the necessary
information can be read from the CD-ROM, thereby
making it possible to greatly reduce the time and
trouble to obtain the necessary information.
BACKGROUND ART
In a conventional CD-ROM which stores the
information related to the dictionary, encyclopedia
or the like, a dictionary file is made up of a
CA 02275391 1999-06-16
-2-
dictionary data and a data related to index
(hereinafter referred to as an index data). For
example, in the case of an encyclopedia, the
dictionary data includes a data (hereinafter
referred to as a text data) related to a text which
explains the meaning of a word, a data (hereinafter
referred to as an image data) related to an image
showing an animal if the 'word describes the animal,
for example, a data (hereinafter referred to as an
audio data) related to a sound such as a singing of
a bird if the word describes the bird, for example,
and the like. On the other hand, the index is used
to retrieve a desired dictionary data from the
dictionary file, and is provided with respect to the
dictionary data. The index is sometimes also
referred to as a keyword. The index data includes a
pointer related to a heading, a pointer related to
an item, and the like. The data related to the
heading includes a headword. Further, the data
related to the item includes a headword, comment,
and the like.
Conventionally, because the storage
capacity of thE: CD-ROM is relatively large, the text
data and the index data are stored in the CD-ROM
without being compressed. On the other hand, the
amount of information included in the audio data and
particularly the image dai=a is large, and the audio
data and the image data are respectively compressed
according to appropriate compression techniques
before being stored in thE: CD-ROM.
However, if one CD-ROM is required for
each dictionary or encyclopedia, it is troublesome
to utilize the dictionary data. For this reason, it
is desirable to store the information related to a
plurality of dictionaries,. encyclopedias or the like
in a single CD-ROM, but in this case, there was a
problem in that: the amount: of information to be
CA 02275391 1999-06-16
-3-
stored may exceed the storage capacity of the single
CD-ROM even if the dictionary data is compressed.
In addition, even in a case where the dictionary
file to be stored in the CD-ROM relates to a single
dictionary, encyclopedia or the like, as the amount
of information of the dictionary file increases, the
amount of information to be stored may exceed the
storage capacity of the single CD-ROM even when the
dictionary data is compressed.
Accordingly, it is conceivable to not only
compress the dlCtionary data but to compress the
entire dictionary file, including the index data,
when storing the informat=Lon related to the
dictionary, encyclopedia or the like in the CD-ROM.
But no method which is capable of efficiently
compressing the entire dictionary file by a
relatively simple technique and capable of expanding
the compressed dictionary file in a short time has
yet been proposed. Particularly in the case of the
dictionary, encyclopedia or the like, the amount of
information related to thE: index data is large. For
this reason, if' it takes a long time to carry out
the process of restoring t:he index data when
expanding the compressed dictionary file, an access
time to the desired index data or dictionary data
becomes long, thereby deteriorating the convenience
of the dictionary, encyclopedia or the like.
Moreover, when compressing the dictionary
data in units of the item of the index or in units
of a fixed length, for example, it takes a long time
to carry out the process of expanding the dictionary
file because th.e amount of information related to
the index data is large particularly in the case of
the dictionary, encycloped~.ia or the like, thereby
similarly deteriorating convenience of the
dictionary, encyclopedia o~r the like. For example,
a Japanese Laid-Open Patent Application No.9-26969
CA 02275391 2003-07-24
27879-153
-4-
proposes a telephone directory retrieval system
which employs a method similar to the above.
However, this proposed method does not compress the
index data. In the case of the telephone directory,
the amount of information related to the index data
is small compared to the amount of information
related to the telephone number, family name, given
name, corporate name and address which correspond to
the dictionary data. Consequently, the information
compression efficiency as a whole will not greatly
improve even if the index data of the telephone
directory were compressed. Therefore, even if this
proposed method were applied to the storage of the
information related to the dictionary, encyclopedia
or the like into the storage medium, the information
compression efficiency of the dictionary file as a
while will not improve considerably.
Accordingly, in a case where the amount of
information related to the index data is relatively
large even when compared to the amount of
information related to the dictionary data, such as
the case of the dictionary, encyclopedia or the like,
there was a problem in that it is conventionally
impossible to efficiently compress and store the
dictionary file in the storage medium and to make
access to the compressed dictionary file in a short
time by a relatively simple process.
DTSGLOSDRE OF THE. INVENTION
Hence, embodiments of the present inv~ntion
provide a file processing method, a
data processing apparatus and a storage medium which
are capable of efficiently compressing and storing a
dictionary file in the storage medium and making
access to the compressed dictionary file in a short
time by a relatively simple process, even in a case
where the amount of information related to an index
CA 02275391 2003-07-24
27879-153
data is large even when compared to the amount of
information related to a dictionary data, such as the case
of a dictionary, encyclopedia or the like.
In one aspect of the present invention there is
5 provided a file processing method comprising: dividing data
and index data different from and corresponding to the data
into a plurality of sections, the index data being used in
searching or retrieving the data and each of the sections
including both data and index data, the data including at
least one element selected from a group consisting of text
data, image data and audio data; compressing the sections to
obtain a compressed file; and storing the compressed file in
a storage medium together with address information of the
sections after the compression.
When each section has a fixed length, it becomes
unnecessary to include address information prior to the
compression in the compressed file, and the data compression
efficiency can be improved. On the other hand, when each
section has a variable length, and said storing step further
stores address information prior to the compression in the
storage medium, it is possible to carry out the data
expansion at a high speed by setting the section to an
appropriate length depending on the data type and section.
When the file processing method further comprises
a restoring step reading the compressed file from the
storage medium and expanding each of the sections, so as to
restore the data and the index data, it is possible to
improve the file retrieval speed by using an auxiliary
storage unit capable of making a high-speed data access and
storing the restored data and index data in the auxiliary
storage unit.
CA 02275391 2004-11-09
27879-153
6
When the compressing step uses a compression
algorithm and a compression parameter which are common to
the data and the index data of each of the sections, it is
possible to simplify the data compression process and the
data expansion process at the time of the data expansion by
using the common compression algorithm and compression
parameter. More particularly, it is possible to use the
Huffman code, the universal code and the like as the
compression algorithm.
In another aspect of the present invention, there
is provided a file processing method comprising: reading a
compressed file from a storage medium together with address
information of each of a plurality of sections after
compression, for each of the sections, said compressed file
being obtained by dividing data and index data different
from and corresponding to the data into the sections, the
index data being used in searching or retrieving the data
and each of the sections including both data and index data,
and compressing the sections, the data including at least
one element selected from a group consisting of text data,
image data and audio data: expanding the compressed file;
and restoring both the data and the index data.
According to the present invention, it is possible
to carry out a high-speed file retrieval by a relatively
simple process, by carry out the expansion of the compressed
file such as a compressed dictionary file for every section.
In a further aspect of the present invention,
there is provided a data processing apparatus comprising: a
compression unit having a computer readable code compression
means for dividing data and index data different from and
corresponding to the data into a plurality of sections, and
for compressing the sections to obtain a compressed file,
CA 02275391 2004-11-09
27879-153
7
each of the sections including both data and index data, the
index data being for use in searching or retrieving the data
and the data including at least one element selected from a
group consisting of text data, image data and audio data;
and a storing unit having computer readable code storing
means for storing the compressed file in a storage medium
together with address information of the sections after
compression.
According to the present invention, it is possible
to efficiently compress and store in the storage medium a
file which is formed by data including an index, text of
each item and the like. In addition, it is possible to
carry out a file retrieval at a high speed by a relatively
simple process, by expanding the compressed file for every
section.
In another aspect of the present invention, there
is provided a data processing apparatus comprising: a
reading unit having a computer readable code reading means
for reading a compressed file from a storage medium together
with .address information of each of a plurality of sections
after compression, for each of the sections, said compressed
file being obtained by dividing data and index data
different from and corresponding to the data into the
sections, and compressing the sections, the index data being
for use in searching or retrieving the data and each of the
sections including both data and index data, the data
including at least one element selected from a group
consisting of text data, image data and audio data; and a
restoring unit having a computer readable code restoring
means for expanding the compressed file and for restoring
both the data and the index data.
CA 02275391 2004-11-09
27879-153
7a
According to the present invention, it is possible
to carry out a high-speed file retrieval by a relatively
simple process, by carry out the expansion of the compressed
file for every section.
CA 02275391 2003-07-24
27879-153
8
In still another aspect of the present invention
there is provided a storage medium which stores computer-
readable information causing a computer to read and restore
a compressed file by: reading a compressed file from a
storage medium together with address information of each of
a plurality of sections after compression, for each of the
sections, said compressed file being obtained by dividing
data and index data different from and corresponding to the
data into the sections, the index data being used in
searching or retrieving the data and each of the sections
including both data and index data, the data including at
least one element selected from a group consisting of text
data, image data and audio data, and compressing the
sections expanding the compressed file; and restoring both
the data and the index data.
According to the present invention, it is possible
to carry out a high-speed file retrieval by a relatively
simple process, by carry out the expansion of the compressed
file for every section.
In a further aspect of the present invention,
there is provided a storage medium which stores computer-
readable information by: dividing data and index data
different from and corresponding to the data into sections,
the index data being used in searching or retrieving the
data and each of the sections including both data and index
data, the data including at least one element selected from
a group consisting of text data, image data and audio data;
compressing each of the sections to obtain a compressed file
by using a compression algorithm and a compression parameter
which are common to both the data and the index data of each
of the sections; and storing the compressed file together
with address information of each of a plurality of the
sections after compression.
CA 02275391 2003-07-24
27879-153
9
According to the present invention, it is possible
to efficiently compress and store a file in the storage
medium. In addition, it is possible to carry out a file
retrieval at a high speed by a relatively simple process, by
expanding the compressed file for every section.
In another aspect of the present invention, there
is provided a storage medium which stores computer-readable
information, including a program which causes a computer to
carry out: a compressing procedure dividing dictionary data
and index data different from and corresponding to the
dictionary data into a plurality of sections, the index data
being used in searching or retrieving the dictionary data
and each of the sections including both data and index data,
the data including at least one element selected from a
group consisting of text data, image data and audio data,
and compressing the sections to obtain a compressed
dictionary file; and a storing procedure storing the
compressed dictionary file in the storage medium together
with address information of the sections after compression.
According to the present invention, it is possible
to retrieve the file at a high speed by carrying out a
relatively simple process.
In still another aspect of the present invention,
there is provided a computer-readable storage medium storing
a compressed file comprising: a compressed data region
storing compressed data obtained by dividing data and index
data different from and corresponding to the data into a
plurality of sections, the index data being using in
searching or retrieving the data and each of the sections
including both data and index data, the data including at
least one element selected from a group consisting of text
data, image data and audio data, and compressing the
CA 02275391 2003-07-24
27879-153
9a
sections; an address information region storing address
information after compression of the sections; and a
compression parameter region storing a compression parameter
used for the compression.
According to the present invention it is possible
to retrieve the file by carrying out a relatively simple
process.
Therefore, according to the present invention,
even in when the amount of information related to the index
data is large even when compared with the amount of
information related to the dictionary data, such as the case
of the dictionary, encyclopedia and the like, it is possible
to efficiently compress and store the file such as the
dictionary file in the storage medium, and the file such as
the compressed dictionary file can be accessed within a
short time by carrying out the relatively simple process.
Other objects and further features of the present
invention will be apparent from the following detailed
description when read in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a system block diagram showing the
general construction of a computer system which employs an
embodiment of a file processing method;
FIG. 2 is a flow chart for explaining a
compression parameter computing process carried out by a
CPU;
FIG. 3 is a diagram showing a data structure of
the compression parameter;
CA 02275391 2003-07-24
27879-153
9b
FIG. 4 is a flow chart for explaining a data
compression process and an address information computing
process carried out by the CPU
CA 02275391 1999-06-16
--10-
FIG. 5 is a flow chart for explaining a
compressed file composing process and a compressed
file storing process carried out by the CPU;
FIG. 6 is a diagram for explaining the
composing of the compressed files;
FIG. 7 is a flow chart for explaining an
index read process carried out by the CPU;
FIG. 8 is a flow chart for explaining a
data expansion process carried out by the CPU; and
FIG. 9 is a flow chart for explaining a
text read process carried out by the CPU.
BEST MODE OF CARRYING OUT THE INVENTTnN
A description will be given of an
embodiment of a file processing method according to
the present invention and an embodiment of a data
processing apparatus acco~_-ding to the present
invention. This embodiment of the file processing
method and this embodimeni= of the data processing
apparatus employ an embodiment of a storage medium
according to the present ~'_nvention. In this
embodiment of the storage medium, the present
invention is applied to a CD-ROM. However, the
present invention is of course similarly applicable
to optical information storage mediums other than
the CD-ROM, magneto-optical storage mediums such as
a magneto-optical disk, magnetic storage mediums
such as a floppy disk, and various kinds of
semiconductor memory devices.
FIG. 1 is a system block diagram showing
the general construction of a computer system
applied with this embodiment of the file processing
method, and corresponds to this embodiment of the
data processing apparatus. The computer system
shown in FIG. 1 generally includes a central
processing unit (CPU) 1, a~ main storage unit 2 made
up of a random access memory (RAM) or the like, an
CA 02275391 1999-06-16
-11-
auxiliary storage unit 3 made up of a hard disk
drive or the like, an input device 4 made up of a
keyboard, mouse or the like, a display unit 5, and a
CD-ROM input/output device 6 made up of a CD-ROM
drive or the like, which are coupled via a bus 9.
Each element itself forming the computer system can
be realized by an element having a known
construction.
The input device 4 is used to input
instructions and data to the CPU 1. The CPU 1
carries out a process requested by a user by
executing a program stored in the auxiliary storage
unit 3 based on the instructions and data which are
input. The program stored in the auxiliary storage
unit 3 may be pre-installed or, may be loaded from a
CD-ROM 6a which is loaded into the CD-ROM
input/output device 6. Tl'ze main storage unit 2 is
used to temporarily store intermediate results of
computing processes or the like carried out by the
CPU 1, data used by the operations, and the like.
The display unit 5 displa~~s a result of the process
carried out by the CPU 1, and messages urging the
user to input an instruction or data. It is
possible to connect a printer (not shown) which
prints the result of the process carried out by the
CPU 1 or the like, in place of the display unit 5 or
in addition to the display unit 5.
First, a description will be given of a
file storing process which stores a dictionary file
of a dictionary, encyclopedia or the like into the
CD-ROM 6a which is loaded into the CD-ROM
input/output device 6. The file storing process
generally includes a compression parameter computing
process, a data compression process for compressing
an index, text and the like, an address information
computing process, a comp~_-essed file composing
process, and a compressed file storing process. In
CA 02275391 1999-06-16
-12-
this embodiment, it is assumed for the sake of
convenience that a progrann for causing the CPU 1 to
carry out the file storing process is stored in the
CD-ROM 6a, and that the CPU 1 reads this program
from the CD-ROM 6a by a known method and loads this
program into the auxiliary storage unit 3. In
addition, it is assumed for the sake of convenience
that the dictionary file related to the dictionary,
encyclopedia or the like is transferred from a host
unit (not shown) and is stored in the auxiliary
storage unit 3 via the bu~> 9 or, read from a CD-ROM
different from the CD-ROM 6a by the CD-ROM
input/output device 6 and is stored in the auxiliary
storage unit 3 via the bust 9.
1a) Compression Parameter Computing
Process:
FIG. 2 is a flow chart for explaining the
compression parameter computing process carried out
by the CPU 1. In FIG. 2, a step S1 makes access to
the auxiliary storage unit. 3 and opens a dictionary
file. A step S2 reads 1 character, that is, a 16-
bit code, for example, from the dictionary file. A
step S3 counts an appearance frequency of the read
16-bit code by use of an appearance frequency
counter within the CPU 1. A step S4 decides whether
or not a last character of the dictionary file is
processed, and the process returns to the step S2 if
the decision result in the step S4 is NO.
On the other hand, if the decision result
in the step S4 is YES, a step S5 closes the
dictionary file. A step S6 sorts the 16-bit codes
depending on the order of the appearance frequency,
and a step S7 selects 1024 16-bit codes, for example,
depending on the order of the appearance frequency.
A step S8 decomposes the remaining non-selected 16-
bit codes into 8-bit codes, and calculates the
appearance frequency of the 8-bit code. A step S9
CA 02275391 1999-06-16
-~ 13 -
corrects the appearance f:cequency of the 8-bit code
with respect to the appearance frequency of the 16-
bit code, by setting the appearance frequency of the
8-bit code to approximate=Ly 1/2.
A step S10 opens a compression parameter
save file for the compression parameter in the
auxiliary storage unit 3. A step S11 writes the
1024 16-bit codes and the appearance frequency
thereof in the compression parameter save file. In
addition, a step S12 writE:s 256 8-bit codes and the
appearance frequency therE:of in the compression
parameter save file. A step S13 closes the
compression parameter savE: file, and the process
ends.
FIG. 3 is a diagram showing the data
structure of the compression parameter. As shown in
FIG. 3, in the case of a compression using the
Huffman code, the compression parameter includes 256
kinds of appearance frequencies for each of the 1024
kinds of 16-bit codes, ancL 256 kinds of appearance
frequencies for each of the 8-bit codes, for example.
The appearance frequencies. become data which are
used to generate a Huffman tree. In the case of a
compression using the universal code, the
compression parameter includes a try tree or data
such as registered symbol examples and reference
numbers thereof which are used to generate the try
tree.
lb) Data Compression Process and Address
Information Computing Process:
FIG. 4 is a flow chart for explaining the
data compression process and the address information
computing process carried out by the CPU 1. In FIG.
4, a step S21 creates a conversion table, that is, a
Huffman tree since this embodiment carries out a
Huffman compression, based on the appearance
frequencies of the 8-bit codes and the 16-bit codes.
CA 02275391 1999-06-16
-14-
A step S22 opens the dictionary file within the
auxiliary storage unit 3. A step S23 opens a
compressed data save file for the compressed data
and an address information save file for the address
information, within the auxiliary storage unit 3.
A step S24 reads 1 section from the
dictionary file. This section may have a fixed
length or a variable length, but in this embodiment,
it is assumed for the sake of convenience that this
section has a fixed length. This section is
sometimes also referred to as a block. A step S25
computes the compressed data of 1 section using the
Huffman tree. A step S26 adds an end code to the
end of 1 section. In addition, a step S27 writes
the compressed data in th~~ compressed data save file.
A step S28 compotes the address
information related to the address where the above
described section is stored. For example, when the
section has the fixed length, the address
information is computed based on a section number
which is assigned with re:~pect to each section. A
step S29 writes the address information in the
address information save :File. A step S30 decides
whether or not a last secition is processed, and the
process returns to the step S24 if the decision
result in the step S30 is N0. For example, it is
possible to decide whether or not the last section
is processed, based on a .Last section code which is
added to the section numbE:r or the last section.
On the other hand, if the decision result
in the step S30 is YES, a step S31 closes the save
file for the compressed data and closes the address
information save file. In addition, a step S32
closes the dictionary file, and the process ends.
lc) Compressed File Composing Process and
Compressed File Storing Pz-ocess:
FIG. 5 is a flow chart for explaining the
CA 02275391 1999-06-16
--15-
compressed file composing process and the compressed
file storing process carried out by the CPU 1. In
FIG. 5, a step S41 opens a compressed file within
the auxiliary storage unit 3. A step S42 opens the
compression parameter save file within the auxiliary
storage unit 3, and a step S43 copies the
compression parameter within the compression
parameter save file to they compressed file. A step
S44 closes the compression parameter save file.
A step S45 opens the address information
save file within the auxiliary storage unit 3, and a
step S46 copies the address information in the
address information save i=ile to the compressed file.
A step S47 closes the address information save file.
Furthermore, a step S48 opens the compressed data
save file within the auxiliary storage unit 3, and a
step S49 copies the comprE:ssed data in the
compressed data save file to the compressed file. A
step S50 closes the compressed data save file. A
step S51 stores the comprE:ssed file in the CD-ROM 6a
by the CD-ROM input/output: device 6. In addition, a
step S52 closes the compressed file, and the process
ends.
FIG. 6 is a diagram for explaining the
composing of the compressed file with reference to
la) the compression parameter computing process, lb)
the data compression process and the address
information computing process, and lc) the
compressed file composing process and the compressed
file storing process described above. In FIG. 6,
(a) shows the compression parameter. In this
embodiment, the compression parameter is used to
carry out the compression using the Huffman code.
In FIG. 6, (b) shows the sections of the dictionary
file. In this embodiment, each section is made up
of 2 kbytes, for example, and each section is made
up of a dictionary data and an index data. In the
CA 02275391 1999-06-16
--16-
case of an encyclopedia, :Eor example, the dictionary
data includes a text data related to a text which
explains the meaning of a word, an image data
related to an image showing an animal if the word
describes the animal, for example, an audio data
related to a sound such as a singing of a bird if
the word describes the bird, for example, and the
like. On the other hand, the index is used to
retrieve a desired dictionary data from the
dictionary file, and is provided with respect to the
dictionary data. The indE:x is sometimes also
referred to as a keyword. The index data includes a
pointer related to a heading, a pointer related to
an item, and the like. The data related to the
heading includes a headword. Further, the data
related to the item includes a headword, comment,
and the like.
In FIG. 6, (c) sohows the compressed data,
in a state where each section has a fixed length or
a variable length and is compressed. Furthermore,
in FIG. 6, (d) shows the address information
computed with respect to each section, and (e) shows
the compressed file which is obtained by composing
the address information anal the compressed data and
adding management information at a head of the
compressed file. The management information
includes information used when retrieving the
compressed file, such as a dictionary file name, a
dictionary file type, and a type of compression used
for the dictionary file.
Next, a description will be given of a
file retrieval process which retrieves a desired
data by reading a compressed file which is stored in
the CD-ROM 6a which is loaded into the CD-ROM
input/output device 6. The file retrieval process
generally includes an index read process and a text
read process, and is carried out by calling a data
CA 02275391 1999-06-16
_17-
expansion process. In this embodiment, it is
assumed for the sake of convenience that a program
for causing the CPU 1 to carry out the file
retrieval process is stored in the CD-ROM 6a, and
that the CPU 1 reads this program and the compressed
file from the CD-ROM 6a by a known method and loads
the read program and compressed file into the
auxiliary storage unit 3.
2a) Index Read Process:
FIG. 7 is a flow chart for explaining the
index read process carried out by the CPU 1. In FIG.
7, a step S61 sets addresa information of a most
significant index, based on the index data input by
the user via the input device 4. A step S62 calls
the expansion process, and reads a routine for
carrying out the expansion process from the program
which is stored in the auxiliary storage unit 3 and
causes the CPU 1 to carry out the file retrieval
process, so as to expand 1=he address of the most
significant index within i~he compressed file. A
step S63 acquires the address of a significant index,
that is, the head charactE:r of the most significant
index, based on the index data. A step S64 calls
the expansion process, an~i expands the address of
the significant index within the compressed file. A
step S65 acquires the address of a less significant
index in a next; hierarchical layer, based on the
index data. A step S66 calls the expansion process,
and expands the address of the less significant
index in the next hierarchical layer described above
within the compressed file:. A step S67 decides
whether or not the expansion of the address of a
least significant index has ended, and the process
returns to the step S65 if' the decision result in
the step S67 is NO. On the other hand, the process
ends if the decision result in the step S67 is YES.
2b) Data Expansion Process:
CA 02275391 1999-06-16
._lg_
FIG. 8 is a flow chart for explaining the
data expansion process carried out by the CPU 1.
The data expansion process is called by the index
read process and the text read process. In FIG. 8,
a step S71 stores the requested expansion address,
data size and storage region in the auxiliary
storage unit 3, based on -the index data which is
input by the user via the input device 4, so as to
prepare a sufficiently large storage region within
the auxiliary storage unfit 3 with respect to the
expanded data size. A stE~p S72 decides whether or
not the compressed file which is read from the CD-
ROM 6a and loaded into thE; auxiliary storage unit 3
i.s open. If the decision result in the step S72 is
NO, a step S73 opens the compressed file within the
auxiliary storage unit 3. A step S74 reads the
compression parameter from the compressed file, and
reads the appearance frequency of the 8-bit code
within the compression parameter, the 16-bit code
within the compression parameter, and the appearance
frequency of the 16-bit co de. A step S75 creates a
Huffman tree based on the appearance frequency of
the 8-bit code and the appearance frequency of the
16-bit code, and the process advances to a step S76
which will be described later. A judging flag for
judging whether the code i.s the 8-bit code or the
16-bit code is added to the data of the leaf of the
Huffman tree .
If the decision result in the step S72 is
YES or after the step S75, the step S76 reads the
address information corresponding to the requested
expansion address, from th.e compressed file. A step
S77 reads the section of the corresponding
compressed data from the compressed file, based on
the address information. A step S78 expands the
section of the compressed data by use of the Huffman
tree. A step S79 copies the expanded data to the
CA 02275391 1999-06-16
._lg_
storage region described above, based on the judging
flag which indicates whether the code is the 8-bit
code or the 16-bit code. Further, a step S80
decides whether or not the expansion of the
requested data size is completed with respect to the
compressed file.
If the decision result in the step S80 is
NO, a step S81 reads the address information
corresponding to the expansion address of the next
section, from the compressed file. The step S82
reads the section of the corresponding compressed
data from the compressed file, based on the address
information corresponding to the expansion address
of this next section, and the process returns to the
step S78. On the other hand, the process ends if
the decision result in thE: step S80 is YES.
2c) Text Read Process:
FIG. 9 is a flow chart for explaining the
text read process carried out by the CPU 1. In FIG.
9, a step S91 counts the items matching the index,
within the expanded data, based on the index data
input by the user via the input device 4. A step
S92 sets a value of an itE:m pointer of the index to
the address, based on the input index data. A step
S93 calls the expansion process, and reads a routine
for carrying out the expansion process from the
program which is stored within the auxiliary storage
unit 3 and causes the CPU 1 to carry out the file
retrieval process, so as t:o expand the text
indicated by the item pointer within the compressed
file, that is, to expand the dictionary data
amounting to 1 section.
A step S94 decides whether or not the
dictionary data indicated by the item pointer has
ended. If the decision result in the step S94 is NO,
a step S95 sets the address of a next 1 section. In
addition, a step S96 calls the expansion process,
CA 02275391 1999-06-16
-20-
and expands the dictionary data amounting to this
next 1 section indicated by the item pointer within
the compressed file, and the process returns to the
step 594. On the other hand, if the decision result
in the step S94 is YES, a step S97 decides whether
or not the process with respect to all of the items
has ended, based on the input index data. The
process returns to the step S92 if the decision
result in the step S97 is NO. On the other hand, if
the decision result in the step 97 is YES, a step
S98 displays on the display unit 5 the dictionary
data which is expanded for all of the items, and the
process ends.
It is possible to carry out the step S98
before the step S97. In this case, the step S98
displays the dictionary data which is expanded for
each item on the display unit 5 each time the
dictionary data is expanded for each item.
In the embodiment described above, it is
assumed for the sake of convenience that the section
has the fixed length. In this case, the data
compression efficiency is satisfactory, and it is
possible to restore the address information from the
compressed file without the need to store the
address information prior to the compression of the
section in the compressed file. This is because the
section has the fixed length, and the section number
is added to each section, thereby making it possible
to calculate a relative position of each section
with respect to another sE:ction.
On the other hand, when the section has a
variable length, it is possible to improve the data
expansion rate. This is because the length of the
section can be set appropriately depending on the
kind of data and section, thereby eliminating the
need to expand excess data. In this case where the
section has the variable length, it is necessary to
CA 02275391 1999-06-16
-21-
store the address prior to the compression of the
section in the compressed file. Accordingly, it is
possible to make the section have the fixed length
or the variable length, depending on whether the
priority is to be given to the data compression
efficiency or the data expansion rate.
In addition, one or more dictionary files
may be stored in the CD-ROM 6a. When a plurality of
dictionary files related to a plurality of
dictionaries, encyclopedias and the like are stored
in the CD-ROM fia, it is possible to specify the
dictionary which is to be retrieved, using the
dictionary file name or the dictionary file type
within the management information shown in (e) of
FIG. 6.
Furthermore, ali~hough the embodiment
described above employs the Huffman code for the
data compression, it is oi: course possible to use
coding techniques other than the technique using the
Huffman code, such as the technique using the
universal code, as long as the employed data
compression technique is capable of efficiently
compressing the dictionary data using a common
compression parameter for each of the sections. In
addition, the data to be subjected to the data
compression and expansion is not limited to the
dictionary data, and includes data of a database
including the index and data.
Moreover, in the: embodiment described
above, the file retrieval process is carried out by
copying the program for carrying out the file
retrieval process and the compressed file to the
auxiliary storage unit 3. However, instead of
copying the program and th.e compressed file to the
auxiliary storage unit 3, it is possible to develop
the program and the compressed file in the main
storage unit 2, and carry out a process similarly to
CA 02275391 1999-06-16
-22-
that described above.
By employing the compression algorithm of
the above described embodiment, it is possible to
improve the data compression efficiency compared to
the normal data compression process using the
Huffman code with 8 bits. As a result, it is
possible to reduce the region of the compressed file
stored in the storage medium such as the CD-ROM and
the hard disk which is used as the auxiliary storage
unit. Although the data compression efficiency is
improved by this compression algorithm, the
processing time required to expand the compressed
file remains essentially unchanged from the
processing time required to expand the compressed
file compressed by the normal data compression
process using the Huffman code.
A time required to carry out the file
retrieval process is made up of a seek time of the
read unit (drive), a read time required to read the
compressed file, and a tirne required to carry out
the expansion process.
Since the data compression efficiency is
improved by the compression algorithm described
above, the reduced region of the compressed file
stored in the storage medp'_um enables reduction of
the seek time of the file retrieval process.
Consequently, the file retrieval speed is improved.
This effect of improving t:he file retrieval speed is
becomes more notable as the hardware performance
improves.
Further, the present invention is not
limited to these embodiments, but various variations
and modifications may be made without departing from
the scope of the present invention.
